“Units attacking Debilitator Alpha get -1 ATK.”
I always assumed the -1 ATK was temporary because it used the present participle (attack-ing). As in, if you’re not an attacking unit, you don’t get the -1 ATK anymore. So once you stop attacking (end of turn) it goes away. (I assumed that it would be permanent if it said, “units that attack Debilitator Alpha…”)
But you’re right that there are a lot of instances where “get” is permanent unless it says otherwise. Behind the Ferns does a continuous check, and it says units with 3 or less ATK “have” stealth, not “get” stealth. So DA could have been worded with “have” instead of “get” and it would be super-clear that it was temporary.
Ferocity, on the other hand, uses “get,” and it’s a one-time assigned thing, and it would be permanent if it didn’t say “until your next upkeep” (just like Rampant Growth, as you mentioned @Coiser). It’s not a continuous check, so if you play a unit after playing Ferocity, you don’t get the effect on that new unit. (It does a one-time check to see what your units are, grants them a one-time permanent bonus, then sets up a condition for that bonus to go away.)
So I would say that you’re right, and that Debilitator Alpha causes permanent debilitation, which is awesome because that makes it a much better card than anyone thought it was, and it might actually see play if ruled that way.