We have had many Israeli-Palestinian peace talks in the past and they are a subject of derision much akin to the UN among more realpolitik thinkers.
We're about to have another one. SecState Kerry seems to have performed some very interesting black magic and it's worth mentioning.
When the last Israeli elections occurred, I was very excited about the possibility of Tzipi Livni winning and immediately pushing for a potentially viable two-state solution. Netanyahu managed to cobble together a coalition government, instead, by pulling in ultra-right-wing zionists, making peace talks seem more-or-less defunct as long as he was in power, particularly as his official policy was that a two-state solution wasn't happening.
Somehow not only the tone, but the official policy, has changed, going into the next talks. Israel released some dozens of Palestinian prisoners and it seems that Likud's (this being Netanyahu's party) new policy is that not only is a two-state solution the answer, but Israel will be willing to make "significant" and "painful" territorial concessions. This is a huge shift and may, again, be part of some John Kerry magic, but good sense is also going to be part of this.
There are obviously major hangups, even in the rhetoric. Likud is also making it clear that Palestine will need to also give significant and painful territorial concessions, which means that Israel will demand that many of the settlements in the West Bank remain--they're a bargaining chip in Israel's favor based on status quo, rather than on any legal or moral argument.
Likud is also saying that Jerusalem will need to keep status quo--meaning Israel gets most of it, but Palestine gets "old town" and some other parts. This on its own is already a concession but may have been necessary for talks to begin.
For a look at settlements, see this link: http://news.bbc.co.uk/2/shared/spl/hi/middle_east/03/v3_israel_palestinians/maps/html/settlements_checkpoints.stm
The settlements are pretty much everywhere throughout the West Bank--it's been akin to a very slow invasion. The blocks near Jerusalem are likely the areas that are going to be the sticking points, as Israel will likely be clear about hanging on to them. Morally I am not fond of these at all but Israel's bargaining power here after the past 30 years or so is so high that at this point it's a geopolitical reality.
Overall the chances of this working are slim, but it may be an example of a "hurting stalemate" that can cause two groups to come to peace even when neither has achieved its political outcome.
Is he serious and if so, why now?
I think Netanyahu is a smart guy. He knows that the conflict has only one long-term possible ending, the two-state solution. Even the slow takeover of the West Bank via settlements would create a long-term painful apartheid, with settlements getting attacked... and he knows that apartheids don't last forever. If Israel totally absorbed the West Bank, it would eventually have to give the Palestinians there citizenship and then the Jews would be outnumbered, and this is obviously unacceptable.
I think the settlements--especially the farther-out ones--are bargaining chips. I think the ones close to Jerusalem are meant to stay and become part of Israel, and I assume that any Palestinians left are going to want to leave to the West Bank when the two-state solution happens (like when India/Pakistan broke up). If Palestine signs the peace deal, it will give Israel legitimacy to whatever territory it keeps.
So I think this has been the long-term plan: to have a two-state solution with added territory for Israel, particularly near Jerusalem. Perhaps now enough of these chips have been accumulated for him to go forward. He knows it will take a long time (maybe years), and probably wants to guarantee that if it does happen, it happens with the best possible terms for Israel, and Netanyahu's "tough guy" reputation means that the Palestinians won't try to over-stretch what they can get out of him for a state.
I think as far as timing, Netanyahu may be taking advantage of Kerry's visit to pretend it changed his mind. I do think that by dumping Shas and picking up both Yesh Atid and Hatnuah (in the 2013 legislative elections) he has to have a coalition that is looking for a two-state solution in earnest... these moderate parties (one led by Tzipi Livni herself) just wouldn't have joined otherwise. It makes him not only free to pursue a two-state solution but I think without it his coalition would fall apart and new elections might be required.
I think ultimately it's up to Netanyahu, rather than Obama/Kerry, as to whether the peace process is going to power forward. If Obama "fails" it will be because Netanyahu--who has all the power and Kerry none--wasn't willing to go forward with the terms that the Palestinians are laying out.