You are 2 models back, with the Roubaix SL4 being the current model.
It looks like half the new Roubaix SL4 bikes are disc bikes. Is that a consideration?
Personally I would keep the old bike, and maintain/upgrade as needed. But, each person is a bit different. You might visit some local bike shops and check out what they have. Perhaps you'd choose a different model. Tarmac?