[EDIT] Looks like we were able to switch completely between the two. Basically there will be two testing windows: one for the 2014 updated Summoner's Rift, and one for the updated Summoner's Rift on the 2015 preseason changes!
Just wanted to give a heads up about some... unique testing we'll be doing on the PBE.
Specifically we've got *two* big projects we want to throw onto the PBE - the 2015 preseason changes, and the updated Summoner's Rift - but both require very different forms of testing. Because of this, we're going to try something different: for the next couple weeks, we'll be **splitting** testing phases into separate sections.
**So here's what you can expect:** On some days you'll be able to play the updated Summoner's Rift with most of what the live environment currently has. On *other* days, you'll be able to play on the updated Summoner's Rift **along with** all of our major 2015 preseason experimental changes, including the updated turrets, jungle changes, dragon changes, and more. We'll be flipping between the two for a few weeks to get extra testing coverage on both, so don't be surprised if things change on the fly.
It's also worth mentioning that stability is one of our core focuses here, so you may not see much iteration between 'phase' shifts. Currently we can't really pin direct PBE dates to when you can expect 2015 season changes + the updated Summoner's Rift vs. just the updated Summoner's Rift, but **if you keep checking back here, we'll keep you posted on the switches**.
You'll see our testing schedules going back to normal roughly after October, but we just wanted to try something new for this month. We appreciate your patience and happy playing!