Does anyone feel like the Assassin update is going to be even more snowbally than ever?

Lethality will be useless so no.

With the possible exception of rengar I doubt it.

Any assassin meta will be more snowbally than most alternative metas because of What assassin's do, but with regards to How they do it, most of these changes seem to reduce rather than increase snowball potential for these individual champions.

I mean, look at LeBlanc and Fizz. They now take a significant amount of time to kill you even if they are ahead, so you can at least run or hope for support or jungle to save you a little more often now.