Maximum Number of Virtual Servers that can be created on BIG-IP LTM 2000S appliance?

There is no defined limit. Object creation is limited only in the amount of space and memory that the configuration requires to store and process objects. A 2000S has the same memory size as the older 6900 and roughly the same capacity. So if I had to take a guess, you'd probably see degradation (ie. slow config updates) between 2000-4000 objects (depending on what's configured).