Just some food for thought. I'll leave you to make up your own mind...
I know my players are old, but they should all be good throughout the season
There is no way to accurately predict the number of skill drops per season for players 33 and older, but you could be correct.
and if I promote, my guards should be able to start for me in D4
My true starting back court has a combined salary of $47,648. My first guard off the bench adds another $11K. You wouldn't be able to train to that level in 1 season, let alone the 4 seasons I've spent training them. With that said, I'm probably only the 6th best team in my league... if that high.
I should make enough money to continue expanding my arena, bringing in even more money through the arena.
I had almost 8K seats in my arena when I promoted, and that's not enough seats to maintain a quality D.IV roster.
and just save up for a good draft pick, then relegate back to D5 with a lot of cash saved up that should be able to get me some nice, younger pieces for the future
Choosing relegation should only be an option when you have hit a wall with your current team, forcing a rebuild. It should never be a part of your building plan, but for sake of discussion, let's break it down.
1. There's no guarantee you will get a good draft pick
2. Relegation has a severe impact on season ticket holders as well as general ticket sales
3. Lower ranked D.IV teams have a better opportunity to make more money than good D.V teams
When that happens, I'll have made enough from staying competitive to pay for one or two young players with good skillsets.
With only a surface glance at your team currently, you would probably be in a relegation position in either division of my league. With the skill drops you'll receive, your team will be in a worse position when/if you promote.
So overall, I think getting a few veterans to promote out of D5 was the right choice, although maybe it would have been better to save up for a few younger guys.
That's the point. You have all older guys with decent skills, then younger guys that can't compete at a D.IV level, but no one in between. Expanding your arena should be the priority right now, then being competitive. I did the same as you when I started. I got my team, then started buying players. The difference is the fact that in my 5th season, I still have 5 of the first 7 players I purchased, and 4 out of the 5 are big contributors still. The other 2 were sold at a nice profit overall. You won't have that option.
I would look towards getting a minimum of 7,500 seats in your arena before you promote. That way, you'll have a strong economy first to fund your plans. The teams that struggle in D.IV are the ones that can't afford to adjust to the competition.
Good luck to you, and I hope your plans succeed.