That is a very interesting question. I would not miss Inle Lake, but neither would I reduce my time in Sri Lanka. I would change my itinerary in Myanmar. You are not doing Sri Lanka the justice it deserves, if you only spend 4 days there.

I was born in Sri Lanka, but have been living in the USA for over 30 years now. Every December I visit Sri Lanka and also include a different country in South East Asia. In December 2014 I visited Myanmar and the highlights of that visit were Inle Lake and Bagan. If I were you, I would fly from Bagan to Heho, as many people have suggested. Also, I would spend less time in Yangon.