Samsung Galaxy S4 will come to T-Mobile on May 1st.

When Samsung announced the Galaxy S 4 they said it would launch in Q2, and now the first US carrier has revealed an actual date. Today T-Mobile announced that the Galaxy S 4 will be available on their network starting May 1. No other US carriers have provided specific launch dates, but we will assume that May will be a popular month to launch the device.
T-Mobile did not reveal their pricing, but the Galaxy S 4 is expected to debut around $579 without a contract. Customers who opt for the equipment installation plan should be able to pick up the GS4 for a $99 down payment, and then owe T-Mobile an additional 24 monthly payments of $20.
The jury is still out on the Samsung Galaxy S 4 vs HTC One debate, but it now appears the HTC One will be the first device available for purchase from US carriers when it launches sometime in April.

Source From: Android and Me.