Microsoft has already started rolling out updates on some selected Lumia models. This is an over the air update that adds 4G functionality on selected Lumia smartphones. Unfortunately it looks like only the 1800 band will be available and there will be no support for 2300 band.
The following smartphones in the Lumia series the Lumia 625, 830, 920, 925, 930, 1320 and 1520 will get the update that will enable 1800 FDD LTE support. Even with this update users in India will not be able to use 4G, cause as of now the network providers are using TDD-LTE 2300 band.
Some users might have already got the update and in case you have not, you will get the notification within few days / weeks. This update only enables 4G feature and does not include any thing else like bug update / additional features etc.
Let us know if you are using any of the above listed handset and if you have got the notification/ updated.