(dis)Advantages of migrating funds to segwit? For offline pre-segwit wallets (addresses starting with 1) what might be the advantages of migrating or not migrating to segwit (addresses starting with 3)?

Even though segwit miner fees are or will be allegedly lower I didn't find any conclusive data on exactly how much lower they are at the moment, therefore I am assuming that keeping coins in 'legacy' format would still be cheaper in terms of future spending since the miner fee for moving to a segwit address would still be significantly higher than any future potential gains. Is this correct? Would this still be true if the coins are going to be spent e.g. in one year, two, or five?

Among current downsides to migrating to segwit wallets I see incomplete support in existing apps, also eg Mycelium won't work with a ledger nano if it is configured as segwit. This subreddit suggests to go with segwit.

Can segwit be considered ready for use?
I am assuming that keeping coins in 'legacy' format would still be cheaper in terms of future spending since the miner fee for moving to a segwit address would still be significantly higher than any future potential gains. Is this correct? 


You still need to move the coins eventually, and the potential gains will be nullified by the fact that you still have to pay BTC in order to move the coins. The amount you pay will probably still be the same amount whether you move the coins now or move them later.

You can also just be very cheap on your transaction fees. Just pay a very low fee rate. Your transaction will take a long time to confirm, but if it's just for cold storage, there's nothing to worry about there.


  Among current downsides to migrating to segwit wallets I see incomplete support in existing apps, eg Mycelium won't work with a ledger nano/trezor if it is configured as segwit.


If you aren't planning on spending your Bitcoin, then that doesn't matter. Just use software that supports segwit. If you want to be compatible with non-segwit wallets, use a P2SH nested segwit address.


  Can segwit be considered ready for use?


Yes.