I don't think you can shift from Maintainence to R&D. Instead, you can shift from R&D to Maintainence. If you are unsure about your future interests, why not taking up R&D at first then see how far you can go ?

It's all down to your goal of your life actually. It's doesn't means that if you got creativity, then you MUST go for R&D. But to be involved in R&D, i Believe you do a lot of creativity and imagination.