I thought of doing that at one time. Win Amp or any player will play movies. So you turn all your backing tracks into movies instead of waves and there's your lyrics. The movie could be a simple as just one or more pages. 
 
Funny thing is back in 1980's when I used my Atari system I had lyric display when the song started. We all used the Pro Midi Player which had the footcontrol and lyric display. Jeff lived here in GRand Forks. He later worked for Roland and designed the editor for the MT 32. 
http://www.jdkoftinoff.com/main/Historic_Projects/The_Pro_MIDI_Player/
 
 
 

I started using the Vocalist and midi-controlled effects units many years ago, so I've been using Cakewalk in performance since pre-Windows days, long before I got my first laptop. I used a looseleaf binder for my lyric/chord sheets, which meant I had to turn pages and select files for every song. When the binder got too big for a single volume, I started looking for a way to do everything on a laptop, and the movie idea was a natural step. My next challenge is to get rid of the keyboard. I'm going to try the touchscreen tablet first, especially since I tend to work without a predetermined setlist, but I'll keep the footswitch idea in mind as an alternative approach.

I'm lucky as I've always had a good memory for lyrics.. nothing else however,,, not good with names or Capital Cities. So I only really need the words for new song for a while and then those I could also remember. As I get older this is of course changing.. faster than I would like. So I'm finding I will need lyrics from now on or make a fool of myself. 
 
The idea of lyrics always poping up when a song is started is definatly the way to go. To bad there really is no software dedicated to live performance. The topic has come up a few times here. 
My wish list. 
4 or so audio tracks is all I would need..even just 2 but seperating Bass would be nice. 
Midi output to control lights, vocal processing and guitar effects or even drive a live instrument
Lyrics pop up when song starts. 
On the fly set list editing, creating and saving. 

personally I don't want the lyrics moved in a "timed" manner, tho, I want to be able to move them from page to page when I am ready; much like powerpoint is done for church congregations.
 
there are few programs which can do that for windows.  there's dozens of them for ipad.
 
last night I just used adobe reader.  it's not elegant and doesn't have all of the bells and whistles that the ipad sheet music readers have (like Forscore) but it worked.  and my AirTurn pedal will advance it, so I guess that's what I'll use.

Nothing wrong with PDF. It can be read by almost any device. Including E readers. 
That was another thing I tried. I have a few E readers kicking around. The screen was just way to small. If I get an iPad it will have to be 10". 
For now the power point is great because you can use the slide sorter to rearrange the songs. I can make and save set lists in Win Amp, then do the same with Power point. I name them so they match. I do like the fact the laptop displaying my lyrics is a 15.5" screen. 
But it's a pita to balance the laptop up high where you can read it, I'm using a x type keyboard stand at it's narrowest setting. Laptops really want to fall over backwards because of the screen. An iPad would be easy to mount on my mike stand. I already have the holder I picked up on a MF stupid deal for $9. If I get the iPad I will also get that footswicth your using. 

iDisplay is one option. If you have an ipad you can hook it up wifi to your computer and use it as a 2nd touch screen monitor. The ipad pro is 12.9".

Cactus Music
Nothing wrong with PDF. It can be read by almost any device. Including E readers. 
That was another thing I tried. I have a few E readers kicking around. The screen was just way to small. If I get an iPad it will have to be 10". 
For now the power point is great because you can use the slide sorter to rearrange the songs. I can make and save set lists in Win Amp, then do the same with Power point. I name them so they match. I do like the fact the laptop displaying my lyrics is a 15.5" screen. 
But it's a pita to balance the laptop up high where you can read it, I'm using a x type keyboard stand at it's narrowest setting. Laptops really want to fall over backwards because of the screen. An iPad would be easy to mount on my mike stand. I already have the holder I picked up on a MF stupid deal for $9. If I get the iPad I will also get that footswicth your using. 

I've been using the 9.7" iPad 4th Gen for almost 4 years every week.  I normally use the iKlip from IK Multimedia to hold it and that way I can bring it really up close to my nose so I can read it because I have trouble reading it at the distance of a music stand - it's right in the spot between the bottom of the bifocal and the distance.  (I tried progressives and never could get used to them).
 
anyway - I've used it for a while, but I have always thought it was too small and wanted something bigger.  I thought about the iPad pro when it came out (12.9") but instead I've jumped back into windows using a 2 in 1 HP laptop.  it folds completely back on itself and has a touchpad screen and it's HUGE (screen size = 15.6"!).  too big and too heavy for the iKlip, tho.  Have to use a music stand.
 
I've only used it for "gigging" once and it worked OK.  but one time is not enough data points!  we'll see how it goes!