I found this on the IK site with some details of ST3:
SampleTank 3 - The main official informational threadby
Peter_IK » Tue Feb 11, 2014 5:48 pm This is a repost from another forum that I feel should definitely also be here on our official forum, I’ve tried to create the most informative possible about SampleTank 3, and I will share information as clearly as possible.
It is true that 2013 came and went and there was no SampleTank 3. For those unaware, there were some issues and we were not able to release it when we expected to. SampleTank 3 was shown at Winter NAMM 2013 in Anaheim, California from which there are multiple videos (and there was also a mistaken product post from a dealer at that time that has since been removed).
Here is the information we’ve presented so far, I will add anything I may have missed later in the thread if necessary:
SampleTank 3 will be 64-bit only, and you will be able to use previous Powered By SampleTank libraries (Miroslav Philharmonik, SampleMoog, SampleTron, Sonik Synth, Xpansion Tanks, etc) inside SampleTank 3 and it will be definitely possible to import SampleTank 2 combis in SampleTank 3.
Why was it decided that SampleTank 3 will be 64-bit and why was SampleTank 2.5 not updated to provide 64-bit compatibility?
See this postThe included library will be over 30GB in size and will include over 3,000 instruments in 20 categories
There are three main sections to the GUI: Play, Mix, and Edit and the new interface is less cluttered with much larger typeface. The Play page has detailed 3D renders of the instruments but can also show a list of the instruments in each slot, volume, pan, MIDI channels, output levels, etc instead.
There will be articulations, round robin, key switching, and velocity switching to bring more realism and control to the SampleTank experience.
The sound quality of the included library is poised to rival that of dedicated libraries while also providing many more of certain types of sounds than the stock library of other products.
SampleTank 3 will include over 50 effects, many of those will be new effects too. There are also effects from flagship products like T-RackS and AmpliTube too. Each of the 16 instrument instrument parts will have 5 insert effects slots. There are 4 stereo FX returns and a Master Channel each with 5 effect slots, too.
There will be 14 types of filters, including analog-modeled filters included.
SampleTank 3 will cost 60% of what SampleTank did when released in 2003 and there will be upgrade pricing, including an extra discount for early adopters of SampleTank 2.
I will add photo and video assets to the thread as time goes, too, this is a good chunk of information to start, though. Thank you for reading.