Will it be Microsoft, JAVA or Someone else?
Software technologies are still in evolving phase so, at this point you cannot say who will be the leader in near future.
We are seeing this question unanswered for many years now. You will get opinions based on what technologies an individual is working. In most cases, it is incorrect because the individual do not understand both technologies equally to be able to make a judgment!
When I was learning .Net in year 2002, there was a big debate if .Net will sustain in the market where JAVA tech was already well established and was widely used. I could notice big resistance in market for .Net. But today we see some of leading .Net products in market and very widely used.
According to me, you cannot answer this question objectively. Answer will vary by domains. You will always see big debate between open source and proprietary product/technology and which one will be a leader in market. In reality, today no major enterprise goes for an open source for its critical requirements for known reasons.
In near future, I see Microsoft and JAVA both sharing the market. Both will have some leading areas for themselves and there will be some common areas as well – People will continue to choose and use either of the technologies based on their requirements and existing systems.