The MVP 2.0 isn't all that old -- yes it was released last year but I believe it was in the late summer / early fall? So I wouldn't expect a new version for at minimum several months from now.
At the price point these things go for, it would be worth it to buy an MVP 2.0 now even if Innokin suddenly surprises us with a new MVP 3.0 next month. They are probably the best value for the money than any other PV.
If and when the MVP 3.0 comes out, then buy one of those and you'll have your MVP 2.0 as its backup.
Really the only feature I would like added to my MVP 2.0 is an extended voltage and wattage range. The MVP 2.0 goes from 3.3 - 5.0 volts and 6.0 - 11.0 watts, and while that is just fine for 95+% of the time, being able to go up to 6 volts and 15 or even 20 watts would be nice to have. A 5 amp limit would also be a nice upgrade over the MVP 2.0's 3.5 amp limit (and a 7.5 amp limit would be awesome), especially if the voltage and wattage range is increased. This of course could only be done if the battery is capable of safely pushing 5 amps or 7.5 amps.
Being able to accept an 18650 battery is something I would want on the MVP 3.0 only if it did not necessitate a size increase in any dimension. One of the greatest things about the MVP 2.0 is its thinness. Despite having an excellent 2600 mAh battery capacity, it is quite thin, pretty narrow, and fits easily in the pocket. Basically, it's a great form factor that, if needed to be changed in order to accept 18650 batteries, would ruin it.