My guess is that AMPLITUBE 5 (possibly under a new name?) is coming.
While both T-Racks and SampleTank have seen upgrades (to versions 5 and 3 respectively), the third flagship app hasn’t. Changing AMPLITUBE 4 will probably mean a “paradigm shift” (as in “changing concepts”), especially if including features like tweaking your amps by changing tubes, preamps, eqs, etc., much like one of IK’s competitor does. That could explain why the red and black teaser pictures show some kind of electronic switch board (the -7 even with a grid layer on top) which resemble quite a bit the background picture of the UI of said competitor’s apps.
As I mentioned in another post (actually a pm to you, Peter), some special features for acoustic guitar/bass/other instruments will hopefully be included in a major upgrade of our beloved AMPLITUBE.