Pompey's relegation was confirmed after they went down 2-1 against Derby at Fratton Park.
Jake Buxton nodded the visitors ahead from a Jamie Ward corner four minutes before the break.
Luke Varney turned on to a pass from Portsmouthsubstitute Marko Futacs after 74 minutes and fired home an equaliser.
But Steve Davies converted a penalty, controversially awarded for a foul on Ward by Jason Pearce, to seal Pompey's fate.
The south coast club's future remains in the balance as they search desperately for a buyer to lead them out of administration.
But Appleton is still ready to take the helm next term, provided he is able to field a competitive side in League One.
He said: "I want to have the tools to do the job properly and I want to be able to work on a level playing field in the division we're going to be working in.
"I've been planning in the back of my mind anyway for the thought of life in League One. I think it would have been stupid of me not to really."
Appleton is bracing himself for a raft of player departures in the summer and expects to oversee a major rebuilding job.
He added: "You're not really sure what type of budget you're going to be working with, although if I was a betting man, I'd guess it'll be less than 50% of what it is now.
"It is difficult and one thing is for sure. I think there will be a lot of players leaving the football club because if we don't do that, there won't be a football club beyond May. I think that's one thing which is going to happen very, very quickly.
"If I have to start with a blank piece of paper with no names on it, so be it; as long as we can shape things for next year."
Derby boss Nigel Clough felt his side could have won more comfortably, but for their lack of firepower.
"If we had done a little bit better with the situations we had, we could have scored more goals," he said.
"That's the thing that's stopping us from getting in the top six really. Our general play was good enough.
"I'm very happy with the majority of the team. It's just in those striking positions where we need to improve.
"We've put in some solid performances and had enough situations early on to go and get a goal before we did.
"Jake Buxton got one from a corner and we haven't scored enough from that type of situation this season."