Viv, it's just a rumor. I've heard they're focusing on cloud computing and scalability. Certainly SQL Server, Oracle or MySQL backend would open up acceptance to rich new customers who are unimpressed by single-database vendors unless the database is the one they favor.
I can tell you that customers in the small and medium business segments are choosing to use cloud computing accounting systems whose backend is stated but of less relevance than the provider's contractual commitments.
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1
