More or less, yes. There's already plenty of snakeoil out there claiming to erase ciphertext or keys anyway - with zero verifiability, and often the claims have been demonstrably false. I could name two right off the bat: Snapchat. Cryptolocker.
If you want ephemeral communications, GPG actually won't do the trick, the public encryption asymmetric subkeys are pretty long-term; ephemeral communications have key lifespans measured in seconds, not months or years. The closest you can get to what you want right now is probably Axolotl as used by TextSecure/Signal, or perhaps OTR, or perhaps Pond: good designs try to not to need to trust third-parties to destroy things and try to instead make sure third-parties don't see things that are too useful to Eve or Mallory in the future. (Even there, metadata is still a nightmarish concern which is hard to protect and very valuable to Eve, sometimes moreso than content.)
Even trusting the first or second party to clear things, you may have some problems. Did you really clear that memory? Are you certain the compiler didn't 'helpfully' optimise out your memset? (See also: explicit_bzero(), etc.) Did Bob secretly take a copy, or can you trust him not to? (You pretty much have to trust Bob to follow the protocol there; that is the impossible problem behind DRM! If Bob wants to cheat, he's got physical access and all the time in the world: he always wins.) And if Bob is honest, if jackboots bust down Bob's door, does Alice still have to worry about a cold-boot attack? (Probably, yes.) Or Mallory playing really dirty and rooting Alice or Bob's machine, which is always, possibly short of the $5 wrench/rubber-hose attack, the easiest route. (See also: Firewire and Thunderbolt DMA attacks, exploitable USB stack bugs, etc.)
It's possible to try to do trusted ICs with tamper-resistant low-retention EEPROM storage, such as you might find on a specialised smartcard/crypto token or TPM - Pond tries to use a TPM's key storage if one's available, I think? - but these devices are often black boxes with far too little external auditing from the good guys and it is something of a blind spot to prove it is above tampering. (There are a couple of open-source efforts to develop trusted cryptography/security cores, including https://cryptech.is/ for example, but verification that hardware objects came from sources and weren't trojaned even as low as at the gate doping level is Very Hard™!; much harder than deterministic assembly/compilation for software.) They may be trusted by some, but they have a long way to go to be trustworthy.
Rolling along with a pretty website is lovely, but doesn't help with any of these problems. Worse, it may give people a false sense of security. Please, no. The doghouse has enough dogs it in already.