We have launched a new site version 2 weeks ago, regularly put a sitemap, Google has indexed all pages, there is still same Page Rank and old positions for some keywords, but Sitelinks are disappeared.

It was probably causes new page names. Previously there was names like page1.php, page2.php and now is /page-1, /page-2 etc...

Should I need to wait or say goodbye to Sitelinks?

If you put 301 redirects on all the old page names you might recover in 4 to 6 months.

Without, it will take years.

It was, staying for a month and I remove it.

They are already disappeared, probably I can't recover them again?

Maybe you will, maybe you won't. Only time will tell.

Chris, they are back! It's not years, but about a month.

Is that with or without redirecting?
and what's the phrase(s) that triggers the sitelinks?

Because it's always very useful to gather this kind information