I read somewhere that if during the course of the year you hit the earned credit target for the following year (for the earnings percentage level that is above your current percentage) that they will increase your percentage immediately, should you hit the required number of earned credits before year's end.

If that is so, does this also apply to this year as well, or does it only apply to when the new earned credit system actually takes affect starting next year?

Many thanks.

Yes.
it applies from the moment you hit your target.

No, of course not. This year you are paid according to the canister. Next year you are paid according to credits.
What they haven't made clear is whether you will get paid a lump sum to cover all the earned credits once you hit a higher level, or if you just get paid at the higher rate from the day you hit that level.
Justice would require that your entire year's earnings are recalculated at the higher rate but there is so little justice around that up to now I didn't think it was worth bothering raising this question.