There's no limit to which you can go in that case, which doesn't sound like a long term solution to me...But.. What do i know.
You can use hardware/internet growth when deciding block size increase, BIP 103 (
https://github.com/bitcoin/bips/blob/master/bip-0103.mediawiki) mention such scenario.
But this idea bring many question/problem with no universal correct answer/solution :
1. What hardware should be used as reference? Raspberry Pi? Newest Intel/AMD processor?
2. Upper limit of the hardware costs used as reference
3. Should we use slowest/average internet growth as reference
4. What if block size growth is too big to the point HDD I/O speed can't keep up and SSD the only option, which makes storage costs growing quickly (e.g. Ethereum blockchain size which is about 3.8TB and grow about 1.6TB in last year)