Stormraider's Surge Changes

So as most of you may know, there's some changes on PBE headed our way to make the other keystones more attractive instead of just putting Thunderlord's on everyone.

Here's the changes to it:

Stormraider's Surge (Cunning, Tier 6) Movement speed bonus increased to 40% from 35% Now also grants 100% slow resistance for 3 seconds Time frame to deal damage increased to 2.5 seconds from 2

The main thing I want to ask about this is the "100% slow resist for 3 seconds". Since it add's slow resist, what happens if you take this keystone and swifty boots? Will the slow resist stack with each other, causing slows to speed you up since you effectively have 125% slow resist? Or has Riot already went ahead of time to fix this. Also, what happens with this mastery, swifty boots, and Master Yi's ult?