Quite possible. I'm not well versed on the EcoServer, but from I'm reading in the OpenScape 4000 V8 presales literature, the EcoServer can handle up to 12,000 users.
"The EcoServer is the new control of the OpenScape 4000. The 19" housing measuring 1.5 height units contains the entire simplex control including the available alarm interfaces and connections for the AP3x00 access points. The EcoServer option supports converged IP requirements involving applications with a large number of analog and TDM devices, DECT applications, or specialized industry sector applications. The new hardware offers new redundancy opportunities, and can be deployed highly scalable and secure in data centers."
You'd be best off consulting with a system engineer to get an official thumbs-up. You'd want to ensure you don't overload the system. There's a document called "Empirical Formula for OpenScape 4000 Project Planning" (A31003-H3180-P100-2-7620). It has the formulas for determining the estimated processor load. They do it on a point basis. The EcoServer can handle 228,000 points. Each device/trunk takes a certain number of points, but you also have to figure in the "mean traffic value per port" and other things that will give you a migraine!
I'm curious what you're doing for RoIP, as I'm a radio guy. We use Raytheon and Vocality devices that connect to the PBX as a SIP connection.
LoPath
Maintain HiPath 4000 V5 & V6, OpenScape Xpert V4, OpenScape Xpressions, OpenScape Contact Center V8, OpenScape Voice V9