My assessment and prediction is actually the result of a straightforward scripturally-based formula from 3rd Nephi 13:1-6:
“Verily, verily, I say that I would that ye should do alms unto the poor; but take heed that ye do not your alms before men to be seen of them; otherwise ye have no reward of your Father who is in heaven.
Therefore, when ye shall do your alms do not sound a trumpet before you, as will hypocrites do in the synagogues and in the streets, that they may have glory of men. Verily I say unto you, they have their reward.
But when thou doest alms let not thy left hand know what thy right hand doeth;
That thine alms may be in secret; and thy Father who seeth in secret, himself shall reward thee openly.
And when thou prayest, thou shalt not do as the hyprocrites, for they love to pray, standing in the synagogues and in the corners of the streets, that they may be seen of men. Verily I say unto you, they have their reward.
But thou, when thou prayest, enter into thy closet, and when thou hast shut thy door, pray to thy Father who is in secret; and thy Father, who seeth n secret, shall reward thee openly.”
From these verses of scripture we derive the following formula: (service x public) + (prayer x public) = mansion, where service = the amount of work freely done for others; public = the amount publicity or credit bestowed; and prayer= the amount and intensity of prayers offered to God.
I don't know how much Mr. Tebow serves others; but I do know he prays in public frequently, and because of where, when, and how he prays, he draws huge amounts of attention to the fact that he prays. When you draw so much attention to where, when, and how you pray that your name becomes a verb, (something I heard in the office last week: “I hate it when athletes feel the need to 'Tebow' after every big play!”), it's a sure sign that you are sacrificing rewards in heaven for rewards on earth.
Doing good works on earth gets you into the Celestial kingdom; how much credit you get for your good works determines the size or your “reward,” colloquially known as your “mansion,” in that kingdom. Hence, while those of us ending up in that kingdom will be familiar with who we meet there, we may be surprised at the size of their mansion. Why? Because during their sojourn on earth, when we knew and loved them, they prayed and served in secret, so God reserved their reward/mansion for heaven.
I don't mean to pick on Mr. Tebow. He is a just a target of opportunity in the line of fire because of how publicly he promotes his prayers. Many famous people doing great things battle the same ironic challenge.
Will I recognize the size of your mansion in heaven? I hope not. Surprise me!