I don't know and I go back and forth on this a lot. A big part of my indecision is how kids will fit in, since it will be so much easier to have only one mature dog when future-kid is a baby.
If kids and life weren't getting in the way, I'd like 2, maybe 3 Welshies. Definitely a female and maybe another male. I kind of enjoy showing and helping to carry on the breed with a nice male, but pretty sure I'm not ready to breed anytime soon, so I might end up not taking a show quality female and just doing obedience/agility type stuff. Ideally, one or more could be a baby Watson if that happens. Either way, I'd like to wait until he's about 4 before adding a puppy. I need time to forget about his adolescence. Welshies tend to get along really well with other dogs, and I know Watson's ideal would involve lots of other dogs for him to play with.
I'd also really love to have a herding breed, maybe an ES, Aussie, or koolie. I love sporting dogs and Welshies in particular, but I think I would also get along really well with certain herding breeds and would like to try it out.
I kind of doubt we will ever have more than 2 dogs, though in the perfect world where I work less and have more time for dog activities, I would love 3 or 4. Maybe 3 would work if one were older and retired from everything except being a companion. I already spend 2-3 evenings a week doing stuff with Watson and even adding one more dog would be a lot. For now, one Welshie is working out really well.