For one thing, the new account could decrease the average age of accounts on your credit reports — a higher average age is generally better for your score. Additionally, if you applied for a private student loan, the application could lead to the lender reviewing your credit history. A record of this, known as a “hard inquiry” or “hard credit check,” remains on your report and may hurt your score a little.
Even if the debt has passed the SOL in your state for suit (variable by state) and even the federal SOL for reporting (roughly 7 years from when the debt discharged) a collector may still pursue you for this money if you owe it. They will just never be able to collect it or report it if you don't allow them to, although they will certainly try and hope you are ignorant enough of the law that they get money from you.
Once your cards and debts are paid off, will you cancel the credit cards? Sure, you get credit cards with zero balances and no bills out of the loan, but one of the biggest problems with debt consolidation loans is that they do nothing to change the behaviors that got you into debt in the first place. Instead, they add another creditor to your pile, and fan the flames of going into debt to pay off more debt. If you even think you might be tempted to use those cards again after paying them off, or if you're using debt consolidation as an easy out or way to avoid really looking at your budget, it's not right for you. The last thing you want is to take out a loan, pay off your cards, and then charge up your cards again—now you've done nothing but dig your hole twice as deep.
With poor credit, you may not be able to get approved for new credit products like credit cards. Although you may still be able to take out an auto loan or a mortgage, you’ll pay a much higher interest rate because of your low credit score. Compared to a borrower with good credit, someone with poor credit can pay $50,000 more in interest on a mortgage. Over an entire lifetime, you could end up paying over $200,000 more in unnecessary interest just because of bad credit.