If it's important to you to wait until he's 2 years old to neuter, and you want a female (which is what I'd recommend - male/female combos are all we've ever done and they've gotten along famously), I would suggest that you wait on getting a second dog. Getting a companion for HIM is not that great a reason for adding to the pack. Now if you or your husband want a companion for YOURSELVES, that's fine! If you decide not to neuter him at all, there's also the option of an earlier spay for the female, like 6 or 7 months old. She may not go into heat until well past then, but you won't know for sure until it happens.
Unfortunately some dogs may not get along, which will make your life exponentially more complicated than it is with just one dog, and it's also possible that your next dog will be more of a project in terms of training and behavior. There just are no guarantees.
No matter what you decide, there's really no hurry, so why not wait until he's a little more mature and his training is further along. The new puppy is going to suck up a lot of your time, so that will take away time from Lincoln.