It's been decreasing ever so slightly since he was announced. Trunks has experienced more of a decrease given that the repaint is almost identical to the original. I'd say as we get closer to the release, Vegeta will decrease in price as well. Mainstream collectors just want a Vegeta, boot tips or not so why pay $200 and up for the original when there's a perfectly good repaint for under $40.
Same is gonna happen with MexiGoku. As SDCC approaches and when Goku is officially on the market, only hardcore collectors are gonna want MexiGoku.
I don't think we can be sure what'll happen until enough consumers actually get their hands on the repaint vegeta and trunks. Overall though, solely because they're legit and not that different, I think the absurd scalping times will be over for a while for these two.
Personally I think the OG trunks is a bigger gap better than the repaint, than in vegeta's case, where I can see people preferring either. The Trunks repaint I'm definitely not feeling. It's not bad, but it's off, it's noticeably less anime accurate, and in general I just prefer the white highlights on the hair.
We also do not know how much units are produced for these, that will matter a LOT. 18 and especially 17 seemed to have small production numbers, as opposed to saiyan saga vegeta or the regular goku from last year, which I saw around for a LONG time for (near) retail price.
How much units they actually produce of these repaints will effect the inflation of the OG releases the most I'd actually wager. Originally Trunks was harder to get than Vegeta, I started when both were out, vegeta was out longer, but much easier to come by. I think that's in part due to stock numbers. If the vegeta repaint gets a higher production run, that + the imo at least lesser accuracy of repaint trunks, kinda make me feel trunks might eventually overtake Vegeta in aftermarket price... On top of that vegeta has more releases and will get more.