I had HELLP at 23 weeks in my first pregnancy, made it to 36 weeks with no problems in my second pregnancy, now having a little drama at 31 weeks in my 3rd but not preeclampsia or HELLP yet. Even if I had to deliver this week, I've still made it 8 more weeks than I did with my first pregnancy.
There are always people who do get sick again, but in general, most women do not get sick again, and the ones that do, get sick later and less severely. Diabetes is a risk factor so that may up your odds, some. And multiples or advanced maternal age would also increase your risks.
Ideally, it would be a good idea to talk to a specialist dealing with high risk pregnancies before you try to conceive again...either a Maternal Fetal Medicine specialist (MFM) or perinatologist (peri). You don't have to be pregnant to see them, and it's actually better to see them pre-conception so you can find someone you are comfortable with, that your OB is comfortable with (if you decide to see both, some people *only* see an MFM/peri if they do deliveries, while other people see both), and they can make a plan for your pregnancy as far as what baselines, underlying condition testing, etc. they want to do before you are pregnant, what (if any) meds they want you taking, how often they will see you and how they will monitor you, etc. And they can look over your history specifically and give you a better estimate on what your odds are.
Me (29) DH (30)
#1-Olivia Caetlyn-9-28-09-9-28-09, 23+2 wks, emergency classic c-section, class I HELLP, IUGR
#2- Lucas Oliver (rainbow baby)- April 2011, 36+2 wks, HELLP and pre-e free! (lovenox and LDA pregnancy)
#3-Matthew, late October 2012...mostly normal, 37 wks, (lovenox and LDA again)
My blog: http://www.butterflies-and-rainbows.blogspot.com/