The TYPO3 core will drop the $GLOBALS[‚TYPO3_DB‘] stuff from the master the moment when TYPO3 8 LTS is released. So if you as an extension maintainer rely on such syntax in one ore more of your extensions, you need to become active now to be ready for the change.
TYPO3 offers you two ways to go.
Update all your $GLOBALS[‚TYPO3_DB‘] to the new syntax as suggested in the previous posts of this blog. Most of your use cases should be covered with that. If you are developing on the current master, everything will be easy, because the Doctrine DBAL framework is already shipped with the core. Every call you fix should work. If you want to maintain your extension for the current LTS as well as for future versions, you need to wait a couple of weeks. It is planned to provide a doctrine adapter extension for 7 LTS to enable a smooth transition path. Only add this extension to your dependencies and you are fine. TYPO3 7 LTS will load the extension, so Doctrine DBAL will be available, TYPO3 8.x will ignore this dependency, because it is not needed there.
The second option is to stay calm and do (mostly) nothing. In a couple of days, TYPO3 will release a “keep the old DB functions available” extension, that should do exactly that. So if you plan (or aren’t able) to do much about your old code, you should just add this extension to the dependencies of your extension. But be aware, that this new extension will not be actively maintained, because it is considered just as a service for those who are dearly in need for it now. So, if you are able to, always choose the first option.
Sorry, no evasive maneuvers available for TYPO3 6.2 LTS. You are on your own.