I guess a good bunch of 747's will continue to fly as cargo aircraft, can't remember where I've seen or read about that but seems the 747 is quite popular in that respect.
parting out aircraft is a lucrative business as well of course.
There are something like 120 sitting in storage at the moment which means there's a lot to chose from when it comes to parts but we all know how supply and demand hits things.
KLM, QANTAS, BA have all phased out their 747 fleets.
As to there use for Cargo - that could the the one thing to keep in the air for years to come. The following link gives a break down.
https://www.telegraph.co.uk/travel/news/747-who-flies-it-how-many-left/
4 of the top 5 operators are purely cargo. The other is Lufthansa which is operating a mixture of 744s and 748s though the 400s are due to leave service by 2025 according to wiki.
But wiki seems to be a bit behind. Two LH 747s were sent to Holland for dismantle and scrap at the start of last month with 3 more to follow (so have probably gone by now).
Lufthansa have also grounded all their A380s, 7 are set for scrapping, the remainder stored in Spain at a location where if they don't return to service they can dismantled in situ.