You can plan for future size, but avoid assuming that the kitten's current measurements predict an exact adult fit. Choose a design with documented dimensions and a route the kitten can use now, while considering the larger resting area it may need later.
A tall adult-sized tree is not automatically accessible to a small kitten, so examine the lower levels and any age-related restrictions in the product instructions. Do not add improvised stepping objects that move or topple. If the model is modular, confirm which approved changes are possible as the cat grows. Recheck fit and movement over time rather than treating the original purchase as permanently suitable. A well-planned choice balances present access with future space, and keeps alternative low resting and scratching options available during the kitten's development.
Record the kitten's measurements and the date rather than relying on a predicted adult breed size alone. Revisit the same entry openings and resting surfaces as growth changes the space available around the cat.
For product comparisons alongside this advice, see Linden wooden cat tower and Arbor Retreat. The details below explain their sizes and uses.
Further reading: cats.org.uk.
Linden wooden cat tower
Arbor Retreat
Floral Canopy