There's two aspects to it:
1/ IMC support for 2950. It's a pretty old switch, which actually makes it _more_ likely to be supported. Worst case it will show up as a generic Cisco device. You can add your own model name mapping if needed. IMC will still do fault, performance polling, etc. Will possibly need tweaking for backups, but probably not.
2/ The above support is independent of SNMPv2 vs v3 - it doesn't make any difference from IMC's perspective. I'm not sure if the 2950 supports v3. I seem to recall it didn't support SSH, so I'm not sure if SNMPv3 is supported. If the switch supports SNMPv3, IMC will be able to poll it.