It's September 15, so it's the official release date for the Moto G4 Play in the US. That this would happen was unveiled at the beginning of the month when the phone went up for pre-order. You can purchase an unlocked G4 Play straight from Motorola's online store for $149.99.
On the other hand, you could go to Verizon's prepaid arm and nab the same smartphone for just $84.99. Although before today Big Red only said it would sell the G4 Play at some point, it's now become available at the carrier too - if you're interested in prepaid plans. And since you're getting it with such an arrangement, you obviously don't need to sign any long-term contracts.
The Moto G4 Play certainly won't impress any specs-fanatics, but it will probably get the basic tasks done without a worry. It has a 5-inch 720p touchscreen, an 8 MP rear camera with LED flash, a 5 MP selfie cam, the Snapdragon 410 SoC (with a 1.2 GHz quad-core Cortex-A53 CPU), 2GB of RAM, 16GB of expandable storage, and a 2,800 mAh battery. It runs Android 6.0.1 Marshmallow.
can the moto g4 prepaid plan phone ever be unlocked to use with another carrier
can be used in other carriers like at&t or cricket like the moto e 2 generation with the app network?
No, you can not, if you buy the pre-paid phone you have to use it as a pre-paid plan for 6 months before you can carry it over to you existing account, I know this first hand as I bought one only to find this out, I returned the phone