Hi there
I would say YES there is a call for it, but then you do need to consider the 'Market' or Clientele your aiming for.
I am a mobile tech, and my clients range from those who are very much into the lastest thing (So Shellac and Gels etc) and on the other side I have a lot of mature clients which also like good old traditional Polish. I find the cost is also a big factor, some of my mature clients like the Shellac or coloured gel but simply can't afford the price tag of it.
So if you think the market you are aiming at will be asking for polish, then yes there is a market out there. I find also a lot of clients are more then happy to keep polish on their toes as it last down there anyway lol, I know you can have more fancy things done using Shellac, Gels and Minx etc but some clients just want the simplicity and value of polish.
Definitely go to the beauty shows and sample different polsihes. I use CND and Misa and love them both.
Good Luck x