That's probably your best choice, I doubt they'll be obsolete for at least 2 years.
It can handle full bandwidth and other than the IPv6 that twc screwed up and has now corrected, as reliable as the 6121-6141's it replaced. We still haven't heard if spectrum will offer modem only or a discount for coam modems.
Some people have gotten the Spectrum 60/6 and 100/6 service but it's unknown what device they got with it, I assume whatever they were leasing from TWC.
My local office said going forward that for Spectrum internet accounts they will only have one option, the Technicolor gateway combo (forget which model, but it was freakin huge). They said that for customers that are internet only and don't want to pay $5 a month for wifi or have their own routers they will only offer the same device and just turn off the wifi capabilities. At least here they no longer offer anything else.
I returned mine the same day and found a great deal on a 6190.
"Backwards compatible" means that you can use a DOCSIS 3 modem in a system constructed and provisioned for DOCSIS 2 modems and the DOCSIS 2 features will work the same in the newer modem. The concept doesn't apply in the reverse direction, at least until Marty McFly gets the DeLorean from "Back To The Future" running again.
I do agree that it doesn't justify TWC's help desk or field techs suggesting that your DOCSIS 2 modem automatically will no longer work on their DOCSIS 3 network. It's just not going to have the later technical features that hadn't been implemented when DOCSIS 2 rolled out. However, not having some of those could create technical incompatibilities, in particular the need for (four) adjacent downstream bonded channels. Further, once the older modem is off the approved list AND not being rented by TWC to any customer, there is no requirement for TWC to maintain the modem-specific provisioning download files or billing codes in their system.