Spoilers from Ausiello!

Question: OK, I’ll bite: Which female character does Blaine mess around with on Glee? —Lynne
Ausiello: Fox’s promo department already spoiled it — he macks on Rachel! It all goes down at what Mercedes refers to as, “The Rachel Berry House Party Train Wreck Extravaganza!”

Question: Any good news on Tina and Artie’s relationship (or lack thereof) on Glee? — Emily
Ausiello: I’ll do you one better: I’ll give you bad news on Tina’s relationship with Mike Chang! When TVLine’s Megan Masters grilled Harry Shun Jr. about the future of Tike/Mina, he replied ominously, “Sometimes when it goes so good, it can go so bad — and I will leave it at that.”

Source: tvline.com