I'm guessing that by 1900 Greece will have control of Macedonia (southern portion centered on Thessaloniki), Cyprus, the remainder of the Aegean Islands, and maybe some parts of Thrace. I do think additional territory will be obtained via war, although not a war where Greece fights the Ottomans one on one, more likely that another power such as Russia starts a war and Greece decides to be opportunistic (or they, along with the UK, France or another Great Power ally start such a war).
Going forward, I also think that Greco-Russian relations will not be very cordial, seeing as Russia offered a smattering of territory to Greece, whereas the UK facilitated the transfer of the Ionian Islands and helped negotiate a treaty that gave the Southern Dodecanese, Epirus and Thessaly to Greece, on top of being Greece's largest trading partner.
So basically, the UK and Greece will likely be best friends for sometime going forward.