Everything you use will finally be available (now) after an upgrade again, with one exception: knotes.
All KDE programs have suitable replacements, all libraries, too.
Should you miss a program, you can easily (re-)install it.
I do know, because I did it - but I did it with aptitude, which resulted in not losing/reinstalling a program, because I could interactively upgrade the components until there was no conflict any longer.