Outsider looking in but I can't even tell the difference between a lot of these models. They need a small-medium-big of each style that they choose to make. That's it. The displacement variations that they sell in order to address licensing restrictions in specific markets (e.g. the 125 and 200 versions of the 390 Duke) shouldn't exist in the markets without those restrictions.
Duke - 990/790
The 790 brought back makes sense. CFMoto released the 800NK this year with the exact same engine, frame and componentry. The 790 re-release is essentially a parts bin resurrection. Also, the non-R 890 vs 790 was silly but there's 'enough' differences between the 990 and the 790 from a rider experience point of view.
790 -> 890 = Euro5 engine with 'model refresh' enhancements
890 -> 990 = all new and Euro5+
390 - India engine size. Already making them and global homolog'd so why not?
250 - Asia engine size. Same story, already making and global homolog'd so why not?
Adventure - 1390 (3 versions) - This is a common idea now. The biggest dig about ADV bike owners was who actually takes their adventure bike off road vs treating it like an SUV?
The S version(street) having the regular version vs the EVO edition (semiactive suspension, radar cruise,AMT(their version of DCT)) is also a legit option according to the very vocal minority.
It also doesn't help that KTM's design philosophy attracts all the crazies. If you check a variety of KTM forums, it's filled with people who'd give their first born to KTM on one day and then self-immolate themselves in protest the next.
I would be in the market for a 990 Duke R or 1390 GT but my 790 Duke is still going strong at 56,200km. It's so hard to justify with the economic outlook as it is to make a purchase though, and I think thats the problem right there.