Learn Finnish: Kaupungin asukasluku tulee ylittämään miljoonan. - The city's population size will exceed a million.

Finnish doesn't have a true future tense, and usually relies on the present tense for future events. However, to emphasize a definitive future prediction, you can use the verb tulla conjugated in the present tense (here, tulee) followed by the third infinitive illative form of the main verb (here, ylittämään).

Why is miljoonan in the genitive case?

The verb ylittää (to exceed) takes a total object here. Because the action of exceeding the one million mark is viewed as a complete action, the object miljoona takes the genitive case, becoming miljoonan.

Could we just say Kaupungin asukasluku ylittää miljoonan instead?

Yes, you absolutely can! Using the standard present tense ylittää is the most common way to express the future in everyday Finnish. Using tulee ylittämään just adds a bit more formal, predictive weight to the statement, which is very common in news, reports, or statistical forecasts.

What are the root words inside the compound noun asukasluku?

It is made up of asukas (inhabitant or resident) and luku (number or count). Put together, it translates directly to the number of inhabitants, or the population size.