I think they are underestimating Abalos.
Quite the contrary, instead of a forced move, I think the resignation of Abalos is a cunning gambit to develop his position as to the eventual criminal trial he will be facing. His term ends February next year (I think) and a few months seem too small a shield to hide behind.
Some people miss the fact that he will be tried while the Arroyo government is in power. Further, he is to be prosecuted by the Ombudsman appointed by PGMA. The same Ombudsman who sat on the Mega Pacific case even if the Supreme Court ordered it to determine who is criminally liable for the fucked-up COMELEC automation project. As expected then, she cleared Abalos.
He resigned to fast-track the criminal cases to be filed against him. He hopes that these criminal cases finish before 2010, or at least the presentation of evidence by the prosecution/Ombudsman. Expect the Ombudsman to file cases against Abalos and expect it to be fast. However, don't expect it to build a solid case that can lead to conviction. It will be bungled and hope that no one will notice the sleigh of hand.
The trial must be finished by 2010, or the prosecution's presentation of evidence at least. If a less sympathetic President is elected in 2010, he knows that while the Ombudsman has a fixed term, the executive has arm-twisting ways to pressure her to resign (just look at how Simeon Marcelo suddenly resigned from office). He isn't taking any chances.
If all goes according to plan, he's scot-free thanks to a weak case presented by the Ombudsman. And we can cry until we can squeeze blood from a stone, until vinegar turns to wine, but double jeopardy will protect him.
Am i glad that he resigned? No. I want him to be prosecuted under a new Administration and not under one that will give him acquittal in a silver platter.