Zillow has a prediction that ought to surprise young people feeling trapped in Boston’s rental cycle: By the end of next year, millennials will overtake Gen X’ers as the country’s biggest bloc of home-buyers.

The company forecasts 2015 will be a promising year for those trying to buy a home for the first time. After looking at factors like income growth, new home construction and increases in rental prices, it’s economists talked directly to potential homebuyers.

“Roughly 42% of millennials say they want to buy a home in the next one to five years, compared to just 31% of Generation X,” said Dr. Stan Humphries, Zillow’s chief economist, in a statement.

“The lack of home-buying activity from millennials thus far is decidedly not because this generation isn’t interested in homeownership,” he said, “but instead because younger Americans have been delaying getting married and having children, two key drivers in the decision to buy that first home. As this generation matures, they will become a home-buying force to be reckoned with.”

Michael Breer, a Boston real estate blogger, sees the same trend locally. “A lot of millennials are coming of age,” he said. Breer, who is also an agent with Sotheby’s International Realty, notes that in the Boston region, banks seem more willing than they were a few years ago to give mortgage loans to millennials – a major hurdle for the first-time home-buyer.

Still, millennials (those under 35 years old) have a lot of ground to make up on Generation X (35-50 years old) and the rest of the U.S. population. A September report from Redfin real estate brokerage said only 42% of millennials nationwide own homes, compared to 65% of the general population.

That gap is much, much bigger in the Boston metro region. According to Zillow’s numbers, only 19% of millennials in Boston, Cambridge and Newton currently own homes, compared to 61% of Gen X’ers and 77% of Baby Boomers. Zillow says the local gulf in ownership is worse than all but five other cities in the whole country.

It’s not a surprise there are relatively few millennial homeowners in Boston, given the competitive market new buyers face. There’s also the problem of matching the high expectations of young people looking to live in trendy areas like the South End, Beacon Hill or Back Bay with the financial realities there.

“You look at the neighborhoods that are desirable for millennials and they’re just not affordable,” said Breer. “Even in a place like Somerville, you’re probably looking at $300,000 to $500,000 for a studio or a one-bedroom.” Breer says under those conditions, young people are likely to rent for a few years in hot neighborhoods before looking to buy somewhere cheaper.

If Boston is going to catch the newly predicted wave of millennial homebuyers, it has to reverse that trend soon, which isn’t likely. For 2015, Boston ranks low among large cities on Zillow’s list of best places for likely first-time buyers – below even notoriously expensive markets like New York and San Francisco.

A big reason Boston is rated as unfavorable to first-time buyers is slow growth in the low-end housing market, a bracket millennials are most likely to land. According to Zillow, Boston has only 6% more units available in that market than it did a year ago. On the other end of the spectrum there’s Las Vegas, which has about 85% more bottom tier homes than it did last October.

Rich Hornblower, a broker with Coldwell Banker who also spoke to Boston.com last month about the tough first-timers market, is holding out hope for the future. He points to a number of projects underway at the Boston Redevelopment Authority, some of which include affordable housing units, as proof the city is trying to attract younger buyers.

“I think as the city keeps on improving and getting better we’re going to see more people trying to set their roots,” Hornblower said. “I think [millennial home ownership] will go up as Boston becomes more of a destination for people trying to stay after college.”

He also thinks young Bostonians will get sick of constantly rising rents and start to long for the stability of a fixed mortgage payment – another major factor in Zillow’s forecast. “They can get a fixed cost, know that they can live in the city and stay there,” Hornblower said. “That’s really valuable versus renting, especially in the downtown area where rents can go up year to year and you have no control over it.”