From what I understand about the Garritan libraries and upgrades and such (with the exception of GOS) they all run in the GPO Kontakt player and simply more folders will be added. That way, you just load whichever instruments you want wherever you want!! And it all is so easy to install and use...yet another beautiful thing about Garritan libraries.
In other words, however many instruments you can use at one time now is the same number you can use with JABB/GPO/GPOA/GSSV of course taking into consideration the size and complexity of the instruments. Some of the saxophones look kinda big with chromaticly sampled key clicks and breath noise (I think that was chromaticly sampled too).