I did some guesswork using the information we know and came up with some predictions on to how far the 2.1~ would take you into level 50+.

Looking at the previous exp increases (no definable pattern I can see) I worked out it will take around 8 million exp to hit level 60.

Level 49 quests give 14,500exp each, so I put level 50 at around 16,000.

If every level 50 quest gave 16,000 you'd be level 52 by the start of Heavensward.

If each new patch gave an increased amount of exp youd gain around 2mil from the quests putting you at level 53.

So if they unlocked the level cap from just owning the expansion you'd enter heavensward at the very least 2 or 3 levels into your cap, This feels fair to me and I can this being the option they take.