Fate/Grand Order has announced that Chapter 4 (99.9% sure it is London) will be coming out late December or early January and will include a ton of highly requested updates and changes. Master Level Limit will be raised beyond 100 which is the current cap—this change opens up a ton of new party composition options that weren't previously possible with the "mana" limit. New Master Options will also be added which allows players to use their Command Seals for other purposes as well as change the equipment of their Master.

The Party Screen has also been changed and will show newly updated art for fully ascended Servants and players will be able to view the level of a Support Servant's Craft Essences. In addition, the maximum party cap will be increased which will make it easier for players to manage and create teams against the new content.

I speculate that the new Master Equipment will be purchasable through the Quartz Shop in the currently empty spot and other speculations include the release of Dr. Jekyll and Jack the Ripper with the London Update due to magazine teasers.

December 13th will also have a maintenance period sometime late at night in JST time which will be upgrading the servers in anticipation of the new event. This is great news (or perhaps bad news if you like apologems like me) as previous events have crushed the servers.

Special thanks to Fate/GO English Twitter for the quick update, and we'll keep you posted of any new information we get!

UPDATE: FGO has announced a compensation of 10 Quartz for the upcoming maintenance which will take place on 12/13 from 8AM PST to 5PM PST.