32 bits ASN on Cisco

Sorry if it is not the right forum, but I'm trying to get a grip on 32Bits ASN on Cisco I see that feature is available on 12.4(24)T http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/ps6554/ps6599/dat... Which is available only for "new gear". I don't know how new is the 1800,2800,3800 series, but I know networks still running on 2500 and 2600. So does it mean that to get 32bit ASN you need to get new gear? Seems to me 12.4(24)T is relatively new, and that this feature is not available on the mainline IOS 12.4? So in one hand RIR allocates 32bit ASN, but on the other hand, it is hard to implement it on current equipment? Is that a (un)fair assessment?