Here is just a list of the phones that will have a Windows Mobile 6.1 Update come the summer.

Samsung ACETM – The Samsung ACE is the sleekest world phone in the Sprint portfolio with a full QWERTY keyboard, vibrant color screen, and ability to use Phone As Modem service.
Moto Q™9c by Motorola – The MOTO Q9c has a slim form factor with a QWERTY keyboard, extended battery, and supports Sprint Navigation for turn-by-turn directions.
Touch by HTC™ – The Touch by HTC is a full touch screen wireless phone with advanced entertainment features. It is the first device to feature TouchFLO™ and features a new HTC-designed homescreen.
Mogul™ by HTC – The Mogul by HTC is the industry’s first EV-DO Rev A-capable handset, enabling users to send and receive large amounts of data at broadband speeds (comparable to basic DSL) and supports Sprint Music Store.
In addition, all of Sprint’s new Windows Mobile smartphones launching in the second half of 2008 will offer Windows Mobile 6.1 software including a new Palm Treo launching later this year. Additional details will be announced upon commercial availability.