50+10? Abandoned or still planned?

The OP asked about level shifts, and ten level shifts were never to my knowledge on the table, and the marketing survey never mentions them.

The devs never considered a level shift itself to be "a level" - that's an invention of the playerbase, something I stated publicly and repeatedly many, many times. The devs originally considered each tier of the incarnate system to be a sort of progressional level, but not an explicit combat level. Level shift was just a specific kind of powerful buff within the system. Even when the real incarnate system was revealed the devs were still referring to the tiers of the system as analogous to incarnate "levels" or progress, with no specific connection to combat level shifts as such.

Both Castle and Black Scorpion confirmed independently to me that there was never any intent to give out ten shifts, or that shifts were supposed to be equated to levels. Also, Castle said it did not occur to him that the players might see incarnate slots with level shift as "a level" while slots without it as "not a level" - there was no intended connection between shifts and incarnate progress in that sense of the word.

50+10 was never planned, never abandoned, and I don't think it was ever seriously contemplated at any time. We aren't going to get it, and at no time was there ever a possibility we were going to get that, at least not in the form they currently take in the incarnate powers (that leaves open the possibility of level shifts as non-perma buffs, ala Ultimate inspirations and the lights in the Magi trial).

The devs can change their minds at any time, but as of right now I would be surprised to see more than one more level shift in the last four slots (most likely in Omega).

The other two have been working just fine for me ever since Dark Astoria happened.

The level shifts, for me, have been inconsequential to everything except for Incarnate content and max difficulty runs. This is largely because I just increase my security level on all my toons that have a shift. So now, I fight at 50+2 instead of 50+1. The powers themselves are what pulls me through difficult situations.

Though I would be lying if I said that the level shifts didn't help me through the I-trials a lot.

Perhaps another measure that could be taken in order to avoid the "player has so many level shifts that older content becomes completely trivial" would be to develop incarnate powers that emulate the effects of Black Swan's quill attack - debuffing level shifts on the most dangerous incarnate foes (even if only for a short while), with a shift "floor" of +0. As there are no special rewards (or at least I haven't noticed any) for defeating a level-shifted foe, such an incarnate power would not be especially overpowering in regular content, but would allow an Incarnate to be far more effective against extremely powerful opponents (Mot, Praetorian Hamidon, etc)

It's probably reasonable that we'll get more toys that allow temporary or conditional level shifts. Powers that boost our shifts for a short time or debuff foes with negative shifts for a short time seem quite reasonable options. Adding mechanics that do that in missions, via granted temp powers or effects like the Light of The Well are pretty good examples, because they keep the level shifts from being something you have to bring on your own.

Imagine a "level shift Build Up". Something like that might be reasonable, and yet still actually pretty powerful both defensively and offensively.