Adding an arm like Hamels can definitely take the Jays to the next level. This team is built to win a championship in 2015, 2016 or 2017. You have Jose Bautista, EE, Donaldson, Martin all locked up in their primes. This is the time to make a run. You are never going to have a core again like Bautista, EE, Donaldson and Martin all at the same time again, and I'm being rational here. There is no way the Jays could sign a FA bat like EE or Bautista on the open market - they got lucky with them as late bloomers and how they signed team friendly contracts, so take advantage of that. Same with trading for JD - players like him aren't made available that often.
Hamels
Hutchison
MB
Dickey
Estrada
And heading into next season, add Stroman to that mix (obviously MB and Dickey could be gone), though a top three of Hamels, Stroman and Hutch looks pretty sweet.