Do you deny that the Buddha spoke this?
http://www.accesstoinsight.org/lib/auth ... .ch23.html
"But, Ānanda, if women had not obtained the Going-forth from the home life into homelessness in the doctrine and discipline made known by the Tathāgata, the holy life would have lasted long, the true Dhamma would have lasted 1,000 years. But now that they have gotten to go forth... this holy life will not last long, the true Dhamma will last only 500 years. Just as a clan in which there are many women and few men is easily plundered by robbers and thieves, in the same way, in whatever doctrine and discipline women get to go forth, the holy life does not last long... Just as a man might make an embankment in advance around a great reservoir to keep the waters from overflowing, in the same way I have set forth in advance the eight rules of respect for bhikkhunīs that they are not to transgress as long as they live." — Cv.X.1
It seems to match as to why Jesus had to come to earth after 500 years, doesn't it?
You have completely misunderstood Buddha's words. I'm obliged to show you the right understanding. Looks like you are misled by your pastor, or whoever, who fed you with all these evangelistic garbage.
First thing, you need to understand the the words 'Going-forth' and 'holy life' which means 'the Sangha' (monkhood). With many women in the Sangha, Buddha foreseen a problem arising in celibacy which is an important precept in 'holy life'. Without any remedy, the holy life a.k.a. the true Dhamma, will last only 500 years.
Therefore Buddha set forth in advance the eight rules of respect for bhikkhunīs that they are not to transgress as long as they live. With these new rules in place, the holy life, the true Dhamma is able to last more than 500 years, 1000 years, 2500 years and longer into the future.
So, please go and tell this to your pastors and church members so that they can stop spewing garbage around to win converts.