I think it's important to recognise that Cell C isn't just offering us better-value data bundles. Not to sound too grandiose, but they're offering us a whole new model of smartphone ownership here.
The essential features of the traditional model:
1. You buy your phone from your cellular network, not from the company that manufactures it (or anyone else).
2. The cost of your phone is subsidised by your network.
3. You're limited to the selection of phones, manufacturers and OSes that is carried by your network.
4. You upgrade on a regular 24 month schedule.
5. You're locked into your contract for the full 24 months.
6. Your network is allowed to make alterations to the phone before they give it to you (eg locking the bootloader, installing bloatware that you can't remove) (note: this isn't such a problem in SA, but it's a very big problem in the US).
7. Software updates have to be tested by the network before they can go out.
Here's the model that Cell C is effectively offering us:
1. You buy your phone from wherever you can get it the cheapest.
2. The full cost of your phone is paid by you.
3. You can choose any phone or OS that supports GSM.
4. You upgrade whenever you feel that an upgrade is necessary, and you're willing to pay.
5. You can leave your contract whenever you want.
6. Your phone comes to you clean, without alterations to the software that the manufacturer installed.
7. Software updates are handled by the manufacturer.
There's nothing new in what you're suggesting, all of the above points have always been valid for prepaid. You didn't have to wait for Cell C to launch new contracts you could experience these 'benefits' at any time with prepaid. The advantage of having a contract at any other network is the subsidy, Cell C don't offer the subsidy, what they're offering is essentially a really good prepaid plan then. Most of us will take the Cell C plan and choose to get our phones on the cheapest contract available elsewhere, the advantage is you no longer have to balance your desire for the newest phone with your need for enough minutes and data - you can have them both, just separately.