I can't recall trying to extend an offline database so what I'd probably do (short of waiting for a definitive answer from someone @ SAP/Sybase ... either here in the forum or from tech support) ...
1 - Assuming you have to perform a full database dump/load after issuing 'alter database', decide on a good time to perform the full database dump/load and then ...
2 - follow your steps (above) and then try restarting the log dump/load and ...
3a - if the log dump/load succeeds ... you've got nothing else to do
3b - if the log dump/load fails, then proceed with the full database dump/load