I always tell clients to book your next cruise onboard your current cruise if you know you want to do another cruise with that same cruise line. It's really tough to beat the lower deposits and the perks you get, so definitely take advantage of it. Besides, worse case scenario, you can always cancel and get a full refund - best of both worlds.
And I'm jealous because because I would love nothing more than doing another Med cruise! Such an awesome place to visit.