For India matches, there'll definitely be a TV broadcast. A very large portion of this Cricket crazy nation is still far away from paid streaming sites, android box/TV and broadband connection. IMO, the percentage is not even 0.01 (1 in 10000) who have all 3 (I've only 2 as of now).
Highly unlikely, as the only possible ROI on that deal is Indian Tour which is only 3 ODI's and a uncertainty over the next Indian tour. May be Amazon will be decided to offer the rights for linear TV if any broadcaster offers heavy undeniable deal. Apart for Indian series I dont see any likely interest from broadcasting perspective. Thats the main reason Star hasn't renewed those rights and opted for CSA, which has certainty of India touring SA.
Amazon might acquire more popular sporting events in future. They are very aggressive in spending money to add contents in prime video. It was over movies mostly but it seems they turned the focus towards live sports. On the other hand, Disney's interaction will stop Star's hard presence in buying rights.