joden
To clarify a post above....it has not a lot to to do with ports. It has everything to do with the number of DRIVERS installed. And yes the limit is still ten, even in W 8.1.

I thought it had been increased to 32 at some point? I have more than 10 drivers installed and they all work. I have run into the MIDI port problem but I suspect it was a lot closer to 32.
 
Here's an article about the MIDI port limit problem, and how to see which MIDI devices Windows sees but you don't. 

Beep - I went thru this exercise on limits a bit back.   http://forum.cakewalk.com/FindPost/3223988
 
What I found is that MIDI is an absolute mess in Windows.  I kindof followed Anderton's article which is based on XP to get to the hidden devices. 
 
As others have said, using a MIDI interface separate from your ASIO audio interface is not a problem
 

There's no difference as far as Windows is concerned between a USB MIDI device and a USB MIDI interface that has multiple MIDI sockets/ports. Some USB connected MIDI controllers have multiple MIDI in/out ports built in which they use for different purposes.

A dedicated MIDI interface counts towards the Wondows devices limit, but the ports it provides do not (as far as I know anyway). I've certainly had more than 10 MIDI ports active at the same time - MOTU MIDI interface with 5 ports, 2 on the UFX, 3 synths/sequencers with USB MIDI connections, internal MIDI virtual cable, control surface...

As for using multiple audio interfaces with ASIO, it's entirely dependant on whether the driver has been written to support this or not. Most drivers don't.

rezab
@ Beepster It is actually almost plug and play. The only issue you could expect is ACT I think.
 
I used to work with a Yamaha 01x, Emu 0404 (I Think) and an Emagic MT4. All working together with several MIDI outboard gear connected to it (This was in my Logic days tho)
 

scook
 Some manufacturers make drivers which communicate with multiple interfaces running concurrently.

@Scooc
WOW you caught my attention!!!!! Please ellaborate. What cards are you talking about? This is pretty interesting functionality... Sorry for going Off Topic.

Most of the major audio interface manufacturers create drivers that allow the same or models in a specific range to work together. RME, Presonus, M-Audio, Tascam, MOTU, Focusrite, Lynx and the list goes on and on. You need to check with the manufacturers on a case by case basis as it does not apply to each model.

@AT @Mudgel
 
WOW, thank you for the revalation. I remember this used not to be the case. You guys made my upgrade (wish/target) list a whole lot affordable.... Thank you.
 
On topic this seemingly simple question turned out in another leson fest for me. 
 
@Beepster, thank you for sharing your question.

I've had M-Audio delta cards when they were first out and their ASIO driver would allow any combination of Delta cards to work together. More than 10 years ago.

Be careful though. As I said previously don't just assume cards will work together. Check with the manufacturer and make sure you use cards from the same manufacturer.

As described above, answers to beepster's a) and b) from post #8 are "yes" and "yes". The Windows wandering usb midi interface problem is not likely to bug you unless you have a lot of USB midi interface devices and a lot of USB ports and you shuffle them around a lot.