After OS 4.5 would be my guess... so perhaps by the end of summer? I rarely dive into the BIS side of the house, aside from a basic configuration of my personal GMail account. I think the trade-off from annual expenses on BES (additional monthly fees for the hosted BES and Enterprise BlackBerry Plan) would leave you more than happy with BIS

...atleast if I had to pay for any of my services, I'd probably feel that way.