Great responses, everyone! Well, until the canon thing, anyway.
I totally forgot to put in my two cents:
If the novelverse were fundamentally contradicted by any new canon, it wouldn't ruin those books for me at all - I still count "The Final Reflection" and "Final Frontier" among my all-time favourites, and events from them can only be imported into the current novel continuity in very broad strokes.
That said, my enthusiasm for future Typhon Pact-continuity novels, as an ongoing series, would probably diminish. That tie-ins tie-in is a big part of their appeal for me. Knowing the fate of Romulus and Spock enhances my enjoyment of the novels featuring them, as I watch the pieces fall into place. If the books say, "oh, thats not our Spock or our Romulus" it would seem.... diminished.