While I don't think that Longbourn itself would be seen as a highly desirable estate by the Bingley girls, it would certainly make Jane a much better catch. Two thousand pounds in income is roughly equivalent a fortune of forty thousand pounds, which is a lot (though only inherited after her father dies, of course). Makes me wonder if the guy who wrote the poetry when Jane was fifteen would have proposed after all. She would be highly sought after from the first, and while that doesn't necessarily mean that she wouldn't still be single by the time Bingley arrives, it reduces the chances.
Unless, of course, Jane was determined to remain single. Because you have to ask yourself what's going to happen if she inherits the estate while married. If it comes to her outright, it then becomes her husband's estate. Even if the estate itself is in trust, to be passed down to her oldest son, the use and income of it would still be at her husband's disposal, unless the legal provisions were very careful and specific. So there's no real guarantee that her husband will be willing to support her mother and four sisters, certainly not at the level that they would wish to be supported. If it all goes to Jane there's no way to divide it and provide for the others, so they're still penniless. Could it be possible that Jane would decide to remain single so that some day she can make sure to provide for her family, or with the intent to sell off parts of Longbourn to provide dowries for the others? But when she meets Bingley she falls in love and thinks that she can surely trust him to do right by her family.
Unless, of course, Jane was determined to remain single. Because you have to ask yourself what's going to happen if she inherits the estate while married. If it comes to her outright, it then becomes her husband's estate. Even if the estate itself is in trust, to be passed down to her oldest son, the use and income of it would still be at her husband's disposal, unless the legal provisions were very careful and specific. So there's no real guarantee that her husband will be willing to support her mother and four sisters, certainly not at the level that they would wish to be supported. If it all goes to Jane there's no way to divide it and provide for the others, so they're still penniless. Could it be possible that Jane would decide to remain single so that some day she can make sure to provide for her family, or with the intent to sell off parts of Longbourn to provide dowries for the others? But when she meets Bingley she falls in love and thinks that she can surely trust him to do right by her family.