Expiration of the START treaty is less than four weeks away. I don't think there is any serious doubt that the new treaty will be signed by that time - although we hear occasional reports about disagreements at the talks, the politics on both sides works for the agreement. Whether it will be a meaningful treaty remains to be seen, but we'll certainly have something.
Once the START treaty expires, its verification procedures will be gone as well. Since ratification of the new agreement will take at least several months, the United States and Russia are facing a "verification gap". With U.S. politics being what it is the gap may easily last for a year or so.
U.S. administration officials have been trying to reassure the public by saying that discussions of temporary measures are underway and that Russia is cooperating. But the details are scarce and nobody seems to have a clear idea of how this "bridging mechanism" would look like.
Some have suggested that the two countries could just agree to abide by the new agreement until it is ratified (or explicitly rejected). This provisional application of the treaty is apparently allowed by the U.S. law as long as no irreversible changes are done. Anyway, I'm sure the U.S. administration could come up with something.
The situation is Russia is a bit more complicated. It appears that any verification or data exchange would require some kind of legal agreement to be in force. For example, the Law on State Secrets (well, you know, Russia does have laws) states that otherwise secret data can be declassified if this is required by Russia's international obligations (Article 13 of the Law). The law is a bit vague on the details (it's a Russian law after all), but it appears that this might take an international treaty signed by the president (Article 4.2). Or it might not - the law appears to give the president some discretion as far as declassification concerned (Article 4.2 again). Or maybe it doesn't. A lot would depend on political will and, apparently, on the willingness of the United States to compromise. In any event, information exchange is the easiest part. When it comes to inspections, it's highly likely that no U.S. inspector would be able to enter Russia until the new treaty comes into force.
So far, the most visible attempt to do something about the upcoming "verification gap" has been a bill, S.2727, introduced by Senator Lugar (via Armscontrolwonk.com) last week. The bill would help make extend the START verification procedures for six months beyond December 5th by providing legal protection to Russian inspectors as long as they carry START inspections. Senator Lugar said in his floor speech that nothing would happen if Russia does not reciprocate (the bill, however, does not say this explicitly). This part makes this whole effort a non-starter - the Russian military are counting the days until December 5th, when the U.S. inspectors will have to leave the Votkinsk plant. They also can't wait to see the end of some START reporting requirements - notifications of mobile missile deployments have emerged as a particularly sore point. Not to mention the expected deployment of RS-24 - Russia would probably not want to submit the technical data on this missile in START format, for it would show that it's essentially a Topol-M.
I guess the only realistic "bridging" solution at this point is to have an executive agreement that would allow provisional application of the new treaty procedures. The laws seem to be flexible enough to give the presidents the authority to do that, although some problems may be expected on both sides. The precedent that was established by START itself, by the way, is not particularly encouraging - there were no inspections or data exchange on provisional basis between July 1991 and December 1994, when the treaty came into force. However, the times were quite different then.
We don't know yet what the new provisions are, but let's hope they are not a big step back from the START ones. In any event, it would be better than living with the verification gap.