From the announcement:
We've given Rampage backers a mini-team of 8 Plague Players AND a mini-team of 8 Mechanite players as we finish Season 4 off in style!
We’re going to be moving on to Season 5 very soon, where Rampage will be able to pick a Season 5 team of your choice as well – if we dare to dream, they’ll be able to do the same with a Season 6 team too!
So what does this mean?
Well, it means Rampage backers keep their ability to get a team of their choice (from Season 5!) AND get two mini-teams bundled in as well. That's 16 more players added to your pledge without you having to lift a finger! Frenzy backers continue to get every teams maxed out at 16 players, plus a load of cool exclusive add-ons and every MVP (plus some other goodies yet to be revealed!) included in their pledge as well.