As an ex-Apple Genius, I can confirm that the MacBook and Newer MBP's (TB) have the SSD's permanently fixed to the Logicboard. There's always cloud based drives, and iCloud that can help to relieve the stress of limited storage, but if you need internal storage, purchase accordingly. It's a lot of money for one of these lovely new machines, don't just purchase on a whim. Know what you are spending all that cheddar on.