Mahesh
I faced a similiar decision a while back. I had a chance to get more heavily involved with voice and i put some serious thought into it as i think there is no doubt voice is a very useful skill to have ie. when i look at the number of jobs here in the UK that ask for voice knowledge there are an awful lot.
Problem was, and i mean no offense to any voice guys reading this , my interests lay elsewhere. I just didn't find it that interesting and it certainly didn't grab my attention in the same way MPLS, for example, did. I am a firm believer in that you should concentrate on what interests you, although obviously if you happen to find token ring and ISDN the most interesting things, you may need to reevaluate as there is not a lot of call for those skills these days.
If you want to learn more IP then i think you have already answered your own question. Undoubtedly voice would make you more marketable for certain jobs but if your heart is not in it then networking will become a chore rather than, hopefully, something you currently enjoy.
Having said that, and in true Cisco legalese, "i am in no way responsible if it so happens that in a years time the only jobs available are voice ones"
Jon
