In a word...yes.

I was worried about the jump from week 3 to 4 also and now I'm going to be working on week 9 tomorrow.  If you are able to complete all three weeks of week 3 then the best thing to do is just move right into week 4.  For me it wasn't as bad as I thought it was going to be and I was able to make it through the week.  Give it a shot and if you don't quite make it and have to repeat a day it's no big deal, but you may surprise yourself.  One thing I did (and still do) is run with a stopwatch.  I would start the time at the beginning of each run and go as long as I thought I could and I wouldn't check my time until then.  Most times I would be surprised to see I had gone 3:30 or 4:00.  By that point I figure I had already gone that far, what's another minute or so?  It made it a lot easier for me seeing that light at the end of the tunnel.