I would like to know this too.
Ledger has stated that adding ERC20 support to ledger live is one of their top priorities currently.
Besides fixing bugs and adding fast and necessary features, this should be pretty far up on their to-do list.
I wouldn't be surprised if we could expect the release of ERC20 supports within a few months.
Ledger has started with ledger live supporting all currencies which have been accessible through their google chrome apps.
Since google is stopping chrome application support, they had to release a software which manages all of these coins first.
They are going to add further coins later on.
Whether they will be releasing the function to import a 'watch' wallet for all coins, or fully functional wallet elements for each currency unfortunately hasn't been stated yet.