I think you've got it exactly right. An Obama "sweep" seems unlikely. A Clinton "sweep" is certainly possible, but it's unlikely she can make up much ground in the delegate race.
(In another example of the small states killing her, the expected size of an Obama win in Vermont may very well win him more delegates there than he will lose in Ohio and Texas.)
The most likely scenario is a muddled result. Clinton will win something somewhere that will give her at least some rationale, at some level, to soldier on.
However, watch for, starting Wednesday, increasing calls from "uncommitted" Democrats for her to fold her tent. The Democrats, facing an increasingly unified McCain candidacy, simply don't want this thing to keep dragging on and on, especially since Pennsylvania is six weeks away.
Plus, the Democrats DO NOT want to have to resolve the Michigan/Florida issue, since there is no good way to resolve it. Uniting behind one candidate now (presumably Obama) renders the Michigan/Florida problem somewhat moot.
There are unconfirmed reports out of the Obama camp that, expecting just that - muddled results on Tuesday and "independent" calls for a Clinton withdrawal starting Wednesday - they have prepared a major offensive later this week to force Clinton out. The first part will be an announcement on Thursday that at least 50 more Superdelegates have committed to Obama (that they've been saving up for just such an announcement). Second, they will announce their previously undisclosed February fund-raising totals which will be well - WELL - north of $50 million, and dwarf Clinton's $35 million.
In other words, the Obama strategy will be exactly what Clinton's strategy was earlier (and didn't work) - project an air of inevitability.
Will it work? Stay tuned.