The problem is, any different method of conveying packets would, by definition, be incompatible with the rules of GSM mobile communication.
Therefore, any manufacturer that doesn't implement the packet transmission scheme exactly as described in this patent, would have to convince all their carrier partners to set up a secondary wireless network, independent of all their existing GSM infrastructure, exclusively for use with that particular manufacture's nonstandard system.
I suppose the manufacturer could omit GPRS (ie. 2G GSM) from their equipment entirely, and stipulate that the phone will only work on networks where UMTS (ie baseline 3G GSM or newer) coverage is available. I haven't read any analysis of how (or if) this patent applies to newer generations of GSM, so I don't know for sure if this would be a viable option.