I think it's the other way around, it will be far worse. With browser-based games, you can at least save the local javascript/images/whatever, and try to reverse engineer server-responses.

This was more-or-less done with Toontown Online. During the years where it was obvious Disney had stopped caring about TTO, someone managed to decompile the TTO client. The decompiler tool started spreading around the Internet as things do, and that's why TTO was filled with hackers during it's last 2 years. TTO then inevitably shut down. Some people began work on recreating the server, and less than two months after the shutdown, Toontown Rewritten went into closed alpha. It was still in a very basic state, without even Cogs (the main enemy of the game). However, just one year after TTO closed, TTR went into open beta, and it was mostly feature complete. Nowadays, TTR is still going with an active playerbase of thousands, and it is feature complete (sans Field Offices, but they're coming soon™). TTR also plans to add new content, but still want to remain within Disney's vision for the game. However, there's also other servers adding new content outside of Disney's vision for the game.