The answer depends on the condition of any park that you are looking at buying now, what the cap rate you are paying for the park and any additional value you can bring to the park to increase its net income. If your park income does not change, then clearly, as interest rates rise, it will sell for less, due to increase in prevailing cap rates. If your rental rates are increasing, depending on how much interest rates rise, it may still sell for less than it is worth currently, sell for the same or sell for more. The hard to impossible part is predicting how much interest rates are going to rise over the next decade and how fast they are going to rise. What you can be relatively certain is that they are not going to improve significantly.
You should be able to predict how much your rents will increase over time and project out your income in the future as MHP_Investor wisely suggested. This will let you create what/if scenarios regarding interest and cap rates to make reasonable guesses at what any given park will be worth in the future.
Although generally, I am a buy and hold investor, and like having income producing properties, I unloaded a large amount of property because, although net cash on cash return was increasing 5%yearly, the cap rates for selling were so ridiculously low, my net profit was so high, it was virtually impossible that rising rental rates would come close to increasing the value of the property to overcome the profit by selling at the cap rate being offered.
I continue to be bullish on parks at what I feel are true 9 and 10 cap rates, especially if they have significant upside. I am not a buyer at a 7-8 cap unless I can see significant upside that will increase the value more than what might be lost with cap rates reverting to more standard norms as interest rates rise. If a person has parks that are full with rental rates at or near market max and ready to sell, now is a great time to be a seller. Just reading today's Wall Street Journal article regarding the GOP proposal to eliminate the interest deduction should be enough to give any real estate investor some increased level of concern about predictability on their investments total returns after taxes. Gringorick has good reason for concern. I am sure that less cautious, overzealous investors will get hurt by rising interests rates due to paying to much for their properties.