It's better if we go with what we have. Even though Berbatov seems likely to leave, Owen's a good backup. Honestly, why buy a striker when we'll have another Berbatov situation, this time with Chicharito or Welbeck? We'll be back to where we were: 4 forwards: Rooney, Welbeck/Chicharito, new striker, Owen.
The reason why Cole, Yorke, Sheringham, and Solskjaer worked so well is because all were at their peaks. None were developing players who needed first-team football to improve their game. They were already fully developed players and thus didn't need regular first-team football to improve but just to keep sharp. That's why they could afford to be rotated.
It's a different scenario with Welbeck and Chicharito. Both are at an age where they will need regular first-team football to improve their game. Why risk that by getting another established striker or Berbatov ahead of both? Both need to develop their game, and regular first-team football is the way to go. Both have had that in spells, whilst 30-year-old Berbatov had to sadly give way to both for their development.
Once both Chicharito and Welbeck are developed, then they can afford to be rotated just like Cole, Yorke, Sheringham, and Solskjaer were.