Hello Mohammed, and welcome to the Cambium Forums!
The ePMP 3000 radio should start shipping by the end of November. Distributors are taking orders now.
The 3000 is planned to have backwards compatibility with older ePMP radios and elevated radios, albeit with a slight performance hit of around 10%. From what I understand, in order for your older radios to be support by the 3000 in backwards compatibility mode, you'll need to update the software on them. More information on this along with new software should come out when they get closer to releasing it.
If I were you, I'd probably buy one unit to test in house with the legacy units you want to use with it. Sometimes it takes awhile and a few software updates to get the best performance and compatibility out of a new product.