Looks great! But I won't update anytime soon. The reasons are:
ST4 won't surpass in sound quality

• TT SD3 for drums
• NI, Ample Sound and Impact Soundworks for bass and guitars
• XLN AK2 for grand piano
• Waves keys for EPs
• NI Session Horns and Magix Independence for pop brass and horns
• KH Orchestra, NI VSL and SoniVox for orchestral instuments
• AiR for synths
• IK ST3 for compact all-in-one rompler

Besides sound quality not being on par with the best instruments on the market, it will take 500GB of disk space (250GB for the sounds, and ~250GB to keep archive available off-line in case you need to re-install it but your download has expired and you need to pay more to download your sounds again).
But it looks like a great investment for those who are new to collecting software instruments. In other words, if I didn't have all other libraries and instruments, I'd bite on the new ST4.  But I do, so I won't.
 

Ditto ^^^^^^

Ditto two here
 

I’ll bite if the upgrade from (full) ST3 to (full) ST4 is under 50 gear credits.
That new piano might just be worth it.

Once you try it, I'll bet a lot of those "won't" entries will turn into "does"... The quality of these sounds is a HUGE leap and is going to be a surprise to many based on the assumptions I'm seeing floating around a couple of forums.

You've convinced me already! What are the timescales for the release by the way? I keep checking my account :)

IK_Multimedia
Once you try it, I'll bet a lot of those "won't" entries will turn into "does"... The quality of these sounds is a HUGE leap and is going to be a surprise to many based on the assumptions I'm seeing floating around a couple of forums.

It's a bit tricky to try a 250GB library for an ordinary user, don't you think? What will the demo contain? How many full instruments, that is, with all samples and articulations, will be in the SE version?

I will most likely get this. I might go for the Max bundle. I have been using ST3 a lot more lately. And as this is really the only "New" sampler that I have (don't have any Kontakt stuff), I have been very satisfied with the sounds for what I do.

But son of a gun, I got a 250gb SSD back a few years ago and never thought I would use it all up, much less need more room, but here I am juggling samples around just to have room!!

Well I made the plunge. Now I gotta install that 1TB SSD I got sitting on the desk.

Soundwise

IK_Multimedia
Once you try it, I'll bet a lot of those "won't" entries will turn into "does"... The quality of these sounds is a HUGE leap and is going to be a surprise to many based on the assumptions I'm seeing floating around a couple of forums.

It's a bit tricky to try a 250GB library for an ordinary user, don't you think? What will the demo contain? How many full instruments, that is, with all samples and articulations, will be in the SE version?

In the cases where users don't have the MAX library when available, and for those that want more information and examples during the pre-order period there will definitely be more videos and audio demos coming.
 
There are over 30 GB of samples and 2,000 sounds in SampleTank 4 SE https://www.ikmultimedia....4/index.php?p=versions
 
The request for more precise lists of sounds (more than the categories and descriptions you can see on the "Sounds" subpage) has definitely been made.  I'll let folks know about that as I have any news.  Thanks!