Indeed, they added envelopes 3 and 4 to the TI in the last TI OS v5 and above.
Of course, don't forget you can use each of the three LFOs as one-shot envelopes, too, which give you up to three envs respectively. The LFO options give you incredible control over start phases, contouring, speed, et al.
On TB-type patches, I use a sine LFO in env mode to very quickly modulate the pitch and filter subtly at note-on, gives the sound an additional little bounce as you hit a key. Would be hard to do with a standard ADSR envelope, as LFOs are animated and bi-polar and they go beyond a standard four-stage envelope.
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PS > And another thing! Will the Ti|3 have user customisable/importable wavetables?
A ribbon-controller or XY-Pad might be nice, too, please! Thanks!