Pokemon Alpha Sapphire / Omega Ruby Online Battles

Solution 1:

Yes,

The 3DS servers are still up and will be up for a while as the 3DS is not meant to compete with the Switch because the Switch isn't as portable as their 3DS console. It would also be a poor decision to discontinue the service when they are still selling the 2DS.

When you no longer see the 2DS for sale you may begin to worry. Most likekly within a few years after the 2DS is no longer for sale they will discontinue their online service as has been the pattern with Nintendo so far... So keep an eye on 3DS/2DS sales figures.

Pokebank should still work though.

To address whether people are still active online the answer is yes. People will play all versions of pokemon forever. Older games are still extremely popular.