I have not found on any of the topics this answer. Maybe I have not looked enough but I didn't find anything. Has Pro changed enough to warrant an upgrade? That is the question.
Frankly spoken, that will depend on your needs mainly. For me the answer is yes, because I work with ProRes (beside XAVC I) and I love the Decklink 4K UHD preview.
That's my issue, pay $349 to upgade from Vegas 11 Pro to Vegas 14 and get very little for it. And then have to pay maybe $199 (assuming updrade deal) to get 15, which will hopefully have features I need. Not going to happen.