I agree that the version numbers are now just irrelevant. I don't think v4 is new, just that v2.5 became labelled v3
Appreciate this is speculation but attached article here states 15hp for Spa and 40hp after that (assume the Sept update as mentioned lots on here). We can guess but the Spa update will have been on the car for the test, between now and then it's about taking the engine apart to see if any reliability improvements are needed.
http://autoweek.com/article/formula-one ... ract-talks
It also mentions that the Honda engine will become within 45hp of Merc/Ferrari after the updates. That's fantastic but still quite a bit to make up and will be the target over the winter, and then Merc/Ferrari won't be standing still either. Honda needs to gain the same again.
However some comments come into proper context now. Alonso's cryptic but positive remarks, the quiet acceptance by McLaren that Honda will be with them in 2018. All these comments over the last week points to Honda revealing to McLaren data from their upcoming developments which have pleased them.
***update*** - looks like same source of info as above post, beat me to it.