Microsoft has two days of big news planned for next week that could include a look at Windows RT tablets and Windows Phone 8.

On Monday, June 18, Microsoft will host a media event in Los Angeles, but the company hasn't provided any other details. An invitation, received by PCWorld and other news outlets, says to expect “a major Microsoft announcement.”

Speculation is already rampant about what the news will be. All Things Digital, citing sources outside Microsoft, claims that the company will demonstrate tablets that run Windows RT, a special version of Windows 8 for ARM-based processors. Although some hardware makers have already announced Windows RT tablets, Microsoft has not yet allowed any hands-on time. That could change next week.

ZDNet's Mary Jo Foley, meanwhile, wonders whether Microsoft will talk about its Xbox Music service. Microsoft announced Xbox Music at its E3 press conference last week, but didn't get into specifics. Los Angeles is an entertainment hub, so the venue makes sense especially if any record companies will be involved in the announcement.

But this mystery press conference isn't the only event Microsoft has planned for next week. On Wednesday, June 20, the company will host a Windows Phone Summit, where it will provide a “sneak peek of the future of Windows Phone.”

PC World