Depends if you're looking to churn and burn or whether the benefits of the platinum card are actually worth the high card fee. If you think the 2-4-1 voucher is valuable there's nothing stopping you from keeping both cards. The platinum card fee is increasing to £650, although the 100,000 points signup bonus more than cancels that out in the first year.

So the long and short of it is, yes get the platinum card for the signup bonus, but you'll need to question whether you renew it past 1 year based on whether the benefits are worth the high fee and if you get value for money.