There are a number of ways to guess in English. Here are some of the most common:

• I'd say he's about ready to quite his job.
• It might need some oil.
• He could be in the garden.
• It looks like a miniature motor.
• Perhaps he needs some time off work.
• Maybe they want to come and visit this summer.
• It's difficult to say, but I'd guess that it's used for cleaning house.
• I'm not really sure, but I think they enjoy hiking in the mountains.