While I do actually like having cash on hand (in lieu of just relying on credit/debit cards), I don't see any reason for Bitcoin to need offline/"cash" style transaction capabilities.

The majority of transactions are already done via cards, which all have to communicate with "the network" as it is. By the time bitcoin were to be big enough for this to be an issue, connectivity will be even greater around the world. Pretty much every vender, or person in general, will have the ability to do online transactions.

There will also assuredly be bitcoin card-scanner type devices, etc.