Will bitcoin core team join bitcoin cash team if the value keeps rising?
I believe that will not happen. They've been on their stance in the past years and I think they will not change sides just because BCH is gaining some price movements and some love from the traders. Don't get confused with this and just check the price of BTC now. It is well above $4k mark and is strongly supported there. Bitcoin core team will not change sides.
BCC was expected to die soon but it has survived theses much days only due to support of some pools like viabtc supporting BCC and some traders doing trade with it to get some quick profits.There is no dedicated supporters for BCC.BCC value is just a speculated value and it does not express its original value.So,in no way,bitcoin core team would join bitcoin cash team.